There are presently various implementations of underwater navigation systems in existence. For example, Doppler sonar devices that contain three or more signal beams are operable in a “Janus” configuration. In a typical Janus configuration, information from each of the signal beams is mathematically combined, and the beam-referenced Doppler velocity measurements are resolved into an orthogonal reference frame. This type of navigation, however, is subject to navigational drift, external environmental conditions, and other types of measurement errors which, when left unattended, lead to inaccurate position, depth, or distance estimates. For example, since two or more beams are combined to compute a single velocity component, errors occurring in the signal beam velocity measurements are not easily detectable, and the resultant reference frame velocity is less accurate. Moreover, velocity bandwidth limitations of the Doppler sonar typically result in erroneous velocity measurements due to signal beam loss or distortion. For example, if one or more of the signal beams become unavailable (for example, due to an obstruction or large attitude excursions causing the beam to not to “see” the bottom of the water body), the velocity measurements are unavailable.
Divers or underwater vehicles that traverse long distances completely underwater are unable to rely on above-surface navigational aids and require an accurate navigation system to arrive at their destination with minimum energy expenditure. There is a need in the art for improvements in underwater navigation.